Despite the misleading name, a black hole is not an empty hole in space, but a highly compressed point of matter with a powerful gravitational field, so much so that even light is not fast enough to escape it. Black holes are the afterlife of stars several times more massive than our solar system’s Sun and have been a source of cosmic mystery for decades[1][2][15].
The existence of black holes was first proposed by a French mathematician by the name of Pierre-Simon Laplace in the 1700s as he imagined the possibility of an object with the peculiar property of having an escape velocity that exceeds the speed of light, valued at 186,000 miles per hour or 300,000 kilometers per second, though he did not refer to that object by its current title of ‘black hole’, a term coined by physicist John Wheeler in the late 1960s. Robert J. Oppenheimer and Hartland Snyder reintroduced the idea into mainstream science after finding that Einstein’s theory of general relativity predicts the objects’ presence. The theory of general relativity tells that gravity can, in a sense, overpower light and bends its path. This lead to the conclusion that there could be an object so massive it can actually trap light. However, the current champion of theoretical physics as it pertains to black holes is Stephen Hawking, the man responsible for a great deal of our knowledge of black holes today.[1][25]
Who's Stephen Hawking?
Stephen Hawking is a renowned theoretical physicist who is responsible for proposing many theories on the origin of the universe, the nature of singularities and black holes. He actually theorized what happened when two black holes would collide based on his past knowledge of, and work on, the topic of singularities, points in the universe at which, as defined by Stephen Hawking,” the fabric of space-time becomes infinitely curved”. In layman’s terms, a point of matter that is so dense that it warps the fabric of space severely. Because of Hawking’s moment of insight, scientists are fairly certain that the result of such a collision would be the creation of a supermassive black hole.[5][6]
He is also to thank for the knowledge that black holes are not immortal, and each will one day die. Hawking concluded, using principles of quantum mechanics, that a black hole will give off radiation during its lifetime, now called Hawking radiation. The radiation and the cosmic giant’s size have an inverse relationship-- as radiation increases, size decreases until the big, bad black hole winks out of existence. In addition to this, Hawking has been involved in a decades long debate on whether or not information is lost in a black hole, a debacle known as the information paradox. After realizing that his initial belief that information was lost--never to be recovered in any form-- in a black hole, Hawking revised his theory and proposed that information was not lost in a black hole. Why? He says that the data will always exist somewhere in the grand scheme of things because, in a parallel world, the black hole that consumed the data does not exist, and therefore, the information is still present. Many physicists go against this belief entirely, claiming that information is not lost at all in any world.[1]
Which was the first?
The first black hole to be discovered was Cygnus X-1 in the 1970s. It was first shown to be part of a binary system—two stars orbiting about each other—but the other star appeared to be missing. Black holes are discovered through indirect observation and radio telescopes. When astronomers noticed that stars seemed to be orbiting an invisible object, it was realized that there was something there, something with a powerful gravitational field. To confirm this, radio telescopes were used to detect the light rays emitted from the black holes. These particular celestial objects are messy eaters. Once cosmic material reaches the event horizon, the apparent ‘point of no return’ when being devoured by the black hole is inevitable, the collected matter is called the accretion disk. As the accretion disk is meets its end, gamma rays and x-rays, the two forms of radiation with the highest energy levels, are given off along with some excess matter, launched at a slower velocity. After decades of using this technique to gauge the location of these high-powered matter-eating monsters, a new way to locate black holes is emerging.[2][9][16]
Black holes are so massive they change the contours of space-time around them, causing a phenomenon known as frame dragging. This, in turn, leads to the distortion of light particles called photons. If this particular form of twisted, rotating light can be detected, a black hole will be as well. Also, the ability to detect this ‘twisted’ light would help scientists find direct evidence as to whether or not black holes rotate, as it is, it has only been assumed that black holes rotate. Another interesting consequence of frame dragging is the effect on time. Once the event horizon of a black hole is approached, time seems to slow down--at least that’s how it seems to an outside observer.[1][3][11]
Image courtesy of Gene Smith, University of San Diego Center for Astrophysics and Space Sciences
Example of how massive objects warp the fabric of spacetime
Matter swirling into a black hole.
This clip is courtesy of NASA Laboratory for High Energy Astrophysics (LHEA)
Formation
Black holes can form in three types of ways. The first, and most well-known, is the result of high energy cosmic event-- a supernova. A supernova occurs when a massive star, many times greater than that of our Sun, reaches the end of its life, when it has run out of hydrogen-- the fuel for nuclear fusion, the star’s energy source-- and sheds its outer layer of matter. Afterward, only the core remains. Under the force of gravity, the core collapses into a dense, pinpoint of matter, a black hole. Less massive cores go on to become neutron stars, incredibly dense stars composed of neutrons that have an unusually strong magnetic field. The second method of black hole formation is through stellar collisions. When a black hole collides with a neutron star, it is thought that a new black hole will appear. The final option for black hole birth is the melding of many black holes into one huge black hole, a supermassive black hole, as Hawking predicted in 1970. An event that will take place once the Andromeda and Milky Way galaxies collide and merge.[2][15][16]
Types
It appears that black holes do not only form in different ways, but also come in different sizes and types-- some theoretical, others proven. There are microscopic black holes, black strings, stellar mass black holes, a strange energetic type called a quasar, and supermassive black holes. Microscopic black holes could be formed by a particle accelerator, such as the Large Hadron Collider, also known as the LHC[14].
Black strings are, in short, hyper-dimensional black holes that could only exist if there were more dimensions of space than meet the eye. They exist in five dimensions, giving them an elongated shape, a bit like a cylinder. Black strings also form the same way as three dimensional black holes, through extreme matter compression, but would be unstable. Any distortion in the string’s shape would cause little,connected black bubbles to form which would then merge into one big black hole[12]
Stellar mass black holes are the type formed from supernovae. Typically, they weigh in at approximately ten to twenty-four times more massive than the Sun. Astronomers believe that there could be millions of stellar mass black holes in our galaxy alone. Some stellar mass black holes are found in binary systems, having a star orbit about.
Quasars, short for quasi-stellar radio source, are thought to be massive black holes that emit vast amounts of radio waves and are the most distant objects astronomers have studied. They are thought to be black holes because only matter being drawn into a black hole can parallel the amount of energy exhibited by a quasar. As a quasar has never been found close to home and are quite rare, they are a bit difficult to study. Some have even suggested that the quasar is a type of galaxy in its own right[1][8][19].
Supermassive black holes are, as stated above, the meshing together of multiple black holes, as is the case when galaxies with black holes at their centers merge.They are extremely massive, having been estimated at millions of solar masses. The best example of supermassive black holes is the one located in the M87 galaxy which is over six billion times the size of our Sun and has an event horizon that is close to three times the size of Pluto’s orbit. They are typically found in the center of large galaxies, even our own Milky Way. However, one has been spotted in a small, dwarf galaxy[17][18].
Wormholes, a favorite method of travel in science fiction, have also been linked to black holes. Wormholes are portals through the universe that are created from the fabric of spacetime being folded, connecting distant areas of space. They were originally known as Einstein-Rosen bridges because they were first theorized by Albert Einstein and fellow physicist Nathan Rosen. They discovered that the theory of general relativity predicted the existence of a kind of cosmic bridge. Together, they discovered that the theory of general relativity predicted the existence of a kind of cosmic bridge. The problem is, these 'cosmic tunnels' are unpredictable and close at any second. Some could even simply exist for less than a second, making the method of travel even less plausible.[7][27]
The closest black hole to our little solar system is Sagittarius A-star, or SgrA*, is the black hole in the center of the Milky Way and has a mass equal to approximately one million solar masses.[23][26]
A graphic representation of a wormhole. Image courtesy of daviddarling.info
How to Find Them
The finding of a black hole in the center of a relatively small neighboring galaxy, Henize 2-10, has shed some light on one of astronomy’s issues--the chicken-and-egg question of what came first, supermassive black holes or their galaxies? The discovery of Henize 2-10’s black hole is cited as further evidence that black holes formed before the galaxies they inhabit. The first bit of evidence used to support this belief was the relationship between the mass of a galaxy’s black hole and the mass of its bulge, or central cluster of stars. The bulge and black hole seem to influence the other’s growth in a galaxy. However, further research has revealed that earlier in the Universe, galaxies in their youth contained black holes that exhibited a larger mass than the present black hole to bulge ratio, supporting the theory that galaxies actually formed after their central black holes[18].
Questions Left Unanswered
Though the knowledge of black holes today is significant, there appears to be many questions left unanswered. How are dark matter and dark energy affected by black holes? What is a white hole? However, as always, there are plenty of theories. Current beliefs are that: 1)The properties of dark matter prevent it from attaining the state necessary for the matter to fall into the black hole. The atoms that make up the matter must have a significantly reduced speed which is achieved through the atoms jostling each other about. Since dark matter doesn’t possess that ability, it cannot spiral down the hole to its doom, 2)Dark energy is a force opposite of gravity--it causes matter to repel rather than attract as gravity does. Therefore, dark energy is unaffected by gravity and will always be able to avoid the fate of ‘normal’ matter and energy. 3)A white hole is the theoretical, and completely unrealistic and nonexistent opposite, of a black hole-- it spews out matter and energy rather than consuming it. There are many more questions that the average person knows nothing of--could not even imagine-- that scientists are asking and attempting to answer. This particular specialization of astrophysics has quite a ways to go.[1][21]
Simple Representation
A Brief Recap
References
Astronomy Department, Cornell University. (n.d.). Black Holes and Quasars. In Curious About Astronomy? Ask an Astronomer. Retrieved from Astronomy Department, Cornell University website: http://curious.astro.cornell.edu/blackholes.php
Black Holes. (2010, September 14). Retrieved from http://science.nasa.gov/astrophysics/focus-areas/black-holes/
Choi, C. Q. (2011, February 15). Findings Could Put a New Spin on Black Holes. Retrieved from http://www.space.com/10831-black-holes-spin-physics.html
Ferguson, K. (1991). Black Holes in Spacetime. New York, NY: Franklin Watts.
Hawking, S. (n.d.). A Comprehensive Glossary. Retrieved from http://www.hawking.org.uk/index.php/glossary
Hawking, S., & Hawking, S. (n.d.). Stephen W. Hawking- My Life in Physics. Retrieved from http://www.hawking.org.uk/index.php/lectures/92
Kaku, M. (2011). Blackholes, Wormholes and the Tenth Dimension. In Welcome toExplorations in Science with Dr. Michio Kaku. Retrieved from http://mkaku.org/home
Library of Past Questions Quasars & Active Galaxies. (1996, September 5). Ask an Astrophysicist. Retrieved from http://imagine.gsfc.nasa.gov/docs/ask_astro/answers/960905.html
Lightman, A. (2005, June). Relativity and the Cosmos. In Einstein’s Big Idea. Retrieved from NOVA website: http://www.pbs.org/wgbh/nova/einstein/relativity/
Masters, K. (n.d.). Curios About Astronomy? Ask an Astronomer [description and Q&A]. Retrieved from Astronomy Department, Cornell University website: http://curious.astro.cornell.edu/question.php?number=353
Matson, J. (2011, February 14). Twisted Light Could Enable Black Hole Detection. Scientific American. Retrieved from http://www.scientificamerican.com/article.cfm?id=twisting-light-oam
Moskowitz, C. (2010, September 22). Black Strings: Black Holes With Extra Dimensions. Retrieved from http://www.livescience.com/ 8656-black-strings-black-holes-extra-dimensions.html
National Geographic. (n.d.). Stars. National Geographic. Retrieved from http://science.nationalgeographic.com/science/space/universe/ stars-article/?source=A-to-Z
O’Neill, I. (2009, November 12). Man-Made(But Very Tiny)Black Holes Possible. Retrieved from Discovery website: http://news.discovery.com/space/the-lhc-black-hole-no-braner.html
Spangenburg, R., & Moser, K. (2004). How Stars Die. In Out of This World Series: The Life and Death of Stars (pp. 73-85). New York, NY: Franklin Watts.
Stars and Their Fates. (n.d.). Stars. Retrieved from http://science.nasa.gov/astrophysics/focus-areas/ how-do-stars-form-and-evolve/
Texas Astronomers “Weigh” Heaviest Known Black Hole in our Cosmic Neighborhood. (2011, January 12). Retrieved from The University of Texas at Austin McDonald Observatory website: http://www.utexas.edu/news/2011/01/12/mcdonald_black_hole/
The National Radio Astronomy Observatory. (2011, January 9). Surprise: Dwarf Galaxy Harbors Supermassive Black Hole. Retrieved from http://www.nrao.edu/pr/2011/bhdwarf/
The StarChild Team. (n.d.). Quasars. Retrieved from High Energy Astrophysics Science Archive Research Center (HEASARC) website: http://starchild.gsfc.nasa.gov/docs/StarChild/universe_level2/ quasars.html
Traschen, J. (2011, January 25). Self-Similar Cascade behavior of Black String Instability. Retrieved from Physics Department, University of Massachusetts Amherst website: http://www.physics.umass.edu/seminars/ self-similar-cascade-behavior-of-black-string-instability
Table of Contents
History
Despite the misleading name, a black hole is not an empty hole in space, but a highly compressed point of matter with a powerful gravitational field, so much so that even light is not fast enough to escape it. Black holes are the afterlife of stars several times
more massive than our solar system’s Sun and have been a
source of cosmic mystery for decades[1][2][15].
The existence of black holes was first proposed by a French mathematician by the name of Pierre-Simon Laplace in the 1700s as he imagined the possibility of an object with the peculiar property of having an escape velocity that exceeds the speed of light, valued at 186,000 miles per hour or 300,000 kilometers per second, though he did not refer to that object by its current title of ‘black hole’, a term coined by physicist John Wheeler in the late 1960s. Robert J. Oppenheimer and Hartland Snyder reintroduced the idea into mainstream science after finding that Einstein’s theory of general relativity predicts the objects’ presence. The theory of general relativity tells that gravity can, in a sense, overpower light and bends its path. This lead to the conclusion that there could be an object so massive it can actually trap light. However, the current champion of theoretical physics as it pertains to black holes is Stephen Hawking, the man responsible for a great deal of our knowledge of black holes today.[1][25]
Who's Stephen Hawking?
Stephen Hawking is a renowned theoretical physicist who is responsible for proposing many theories on the origin of the universe, the nature of singularities and black holes. He actually theorized what happened when two black holes would collide based on his past knowledge of, and work on, the topic of singularities, points in the universe at which, as defined by Stephen Hawking,” the fabric of space-time becomes infinitely curved”. In layman’s terms, a point of matter that is so dense that it warps the fabric of space severely. Because of Hawking’s moment of insight, scientists are fairly certain that the result of such a collision would be the creation of a supermassive black hole.[5][6]
He is also to thank for the knowledge that black holes are not immortal, and each will one day die. Hawking concluded, using principles of quantum mechanics, that a black hole will give off radiation during its lifetime, now called Hawking radiation. The radiation and the cosmic giant’s size have an inverse relationship-- as radiation increases, size decreases until the big, bad black hole winks out of existence. In addition to this, Hawking has been involved in a decades long debate on whether or not information is lost in a black hole, a debacle known as the information paradox. After realizing that his initial belief that information was lost--never to be recovered in any form-- in a black hole, Hawking revised his theory and proposed that information was not lost in a black hole. Why? He says that the data will always exist somewhere in the grand scheme of things because, in a parallel world, the black hole that consumed the data does not exist, and therefore, the information is still present. Many physicists go against this belief entirely, claiming that information is not lost at all in any world.[1]
Which was the first?
The first black hole to be discovered was Cygnus X-1 in the 1970s. It was first shown to be part of a binary system—two stars orbiting about each other—but the other star appeared to be missing. Black holes are discovered through indirect observation and radio telescopes. When astronomers noticed that stars seemed to be orbiting an invisible object, it was realized that there was something there, something with a powerful gravitational field. To confirm this, radio telescopes were used to detect the light rays emitted from the black holes. These particular celestial objects are messy eaters. Once cosmic material reaches the event horizon, the apparent ‘point of no return’ when being devoured by the black hole is inevitable, the collected matter is called the accretion disk. As the accretion disk is meets its end, gamma rays and x-rays, the two forms of radiation with the highest energy levels, are given off along with some excess matter, launched at a slower velocity. After decades of using this technique to gauge the location of these high-powered matter-eating monsters, a new way to locate black holes is emerging.[2][9][16]
Black holes are so massive they change the contours of space-time around them, causing a phenomenon known as frame dragging. This, in turn, leads to the distortion of light particles called photons. If this particular form of twisted, rotating light can be detected, a black hole will be as well. Also, the ability to detect this ‘twisted’ light would help scientists find direct evidence as to whether or not black holes rotate, as it is, it has only been assumed that black holes rotate. Another interesting consequence of frame dragging is the effect on time. Once the event horizon of a black hole is approached, time seems to slow down--at least that’s how it seems to an outside observer.[1][3][11]
Example of how massive objects warp the fabric of spacetime
Matter swirling into a black hole.
This clip is courtesy of NASA Laboratory for High Energy Astrophysics (LHEA)
Formation
Black holes can form in three types of ways. The first, and most well-known, is the result of high energy cosmic event-- a supernova. A supernova occurs when a massive star, many times greater than that of our Sun, reaches the end of its life, when it has run out of hydrogen-- the fuel for nuclear fusion, the star’s energy source-- and sheds its outer layer of matter. Afterward, only the core remains. Under the force of gravity, the core collapses into a dense, pinpoint of matter, a black hole. Less massive cores go on to become neutron stars, incredibly dense stars composed of neutrons that have an unusually strong magnetic field. The second method of black hole formation is through stellar collisions. When a black hole collides with a neutron star, it is thought that a new black hole will appear. The final option for black hole birth is the melding of many black holes into one huge black hole, a supermassive black hole, as Hawking predicted in 1970. An event that will take place once the Andromeda and Milky Way galaxies collide and merge.[2][15][16]
Types
It appears that black holes do not only form in different ways, but also come in different sizes and types-- some theoretical, others proven. There are microscopic black holes, black strings, stellar mass black holes, a strange energetic type called a quasar, and supermassive black holes. Microscopic black holes could be formed by a particle accelerator, such as the Large Hadron Collider, also known as the LHC[14].
Black strings are, in short, hyper-dimensional black holes that could only exist if there were more dimensions of space than meet the eye. They exist in five dimensions, giving them an elongated shape, a bit like a cylinder. Black strings also form the same way as three dimensional black holes, through extreme matter compression, but would be unstable. Any distortion in the string’s shape would cause little,connected black bubbles to form which would then merge into one big black hole[12]
Stellar mass black holes are the type formed from supernovae. Typically, they weigh in at approximately ten to twenty-four times more massive than the Sun. Astronomers believe that there could be millions of stellar mass black holes in our galaxy alone. Some stellar mass black holes are found in binary systems, having a star orbit about.
Quasars, short for quasi-stellar radio source, are thought to be massive black holes that emit vast amounts of radio waves and are the most distant objects astronomers have studied. They are thought to be black holes because only matter being drawn into a black hole can parallel the amount of energy exhibited by a quasar. As a quasar has never been found close to home and are quite rare, they are a bit difficult to study. Some have even suggested that the quasar is a type of galaxy in its own right[1][8][19].
Supermassive black holes are, as stated above, the meshing together of multiple black holes, as is the case when galaxies with black holes at their centers merge.They are extremely massive, having been estimated at millions of solar masses. The best example of supermassive black holes is the one located in the M87 galaxy which is over six billion times the size of our Sun and has an event horizon that is close to three times the size of Pluto’s orbit. They are typically found in the center of large galaxies, even our own Milky Way. However, one has been spotted in a small, dwarf galaxy[17][18].
Wormholes, a favorite method of travel in science fiction, have also been linked to black holes. Wormholes are portals through the universe that are created from the fabric of spacetime being folded, connecting distant areas of space. They were originally known as Einstein-Rosen bridges because they were first theorized by Albert Einstein and fellow physicist Nathan Rosen. They discovered that the theory of general relativity predicted the existence of a kind of cosmic bridge. Together, they discovered that the theory of general relativity predicted the existence of a kind of cosmic bridge. The problem is, these 'cosmic tunnels' are unpredictable and close at any second. Some could even simply exist for less than a second, making the method of travel even less plausible.[7][27]
The closest black hole to our little solar system is Sagittarius A-star, or SgrA*, is the black hole in the center of the Milky Way and has a mass equal to approximately one million solar masses. [23] [26]
How to Find Them
The finding of a black hole in the center of a relatively small neighboring galaxy, Henize 2-10, has shed some light on one of astronomy’s issues--the chicken-and-egg question of what came first, supermassive black holes or their galaxies? The discovery of Henize 2-10’s black hole is cited as further evidence that black holes formed before the galaxies they inhabit. The first bit of evidence used to support this belief was the relationship between the mass of a galaxy’s black hole and the mass of its bulge, or central cluster of stars. The bulge and black hole seem to influence the other’s growth in a galaxy. However, further research has revealed that earlier in the Universe, galaxies in their youth contained black holes that exhibited a larger mass than the present black hole to bulge ratio, supporting the theory that galaxies actually formed after their central black holes[18].
Questions Left Unanswered
Though the knowledge of black holes today is significant, there appears to be many questions left unanswered. How are dark matter and dark energy affected by black holes? What is a white hole? However, as always, there are plenty of theories. Current beliefs are that: 1)The properties of dark matter prevent it from attaining the state necessary for the matter to fall into the black hole. The atoms that make up the matter must have a significantly reduced speed which is achieved through the atoms jostling each other about. Since dark matter doesn’t possess that ability, it cannot spiral down the hole to its doom, 2)Dark energy is a force opposite of gravity--it causes matter to repel rather than attract as gravity does. Therefore, dark energy is unaffected by gravity and will always be able to avoid the fate of ‘normal’ matter and energy. 3)A white hole is the theoretical, and completely unrealistic and nonexistent opposite, of a black hole-- it spews out matter and energy rather than consuming it. There are many more questions that the average person knows nothing of--could not even imagine-- that scientists are asking and attempting to answer. This particular specialization of astrophysics has quite a ways to go.[1][21]
Simple Representation
A Brief Recap
References
Horizon: Discovering Black Holes in Centers of Galaxies. Retrieved from
http://library.thinkquest.org/25715/discovery/index.htm
Discovery Communications.
General Relativity & Black Holes. Retrieved May 10, 2011, from
http://cass.ucsd.edu/archive/public/tutorial/GR.html
http://imagine.gsfc.nasa.gov/docs/ask_astro/answers/961130b2.html
http://www.pbs.org/wnet/hawking/strange/html/wormhole.html